1. Technical Field
This disclosure relates to product packaging devices, and more particularly, to a heat sealer device which provides for easier sealing of clam shell-type plastic packages.
2. Description of the Related Art
One important aspect of manufacturing products includes the packaging in which the product is shipped and presented for sale. The packaging in which a product is placed needs to be secure enough to prevent unwanted tampering of the product. In addition, packaging is functional as well. For example, in many applications the packaging provides protection during shipping and during display of the items in for example a store. Packaging further serves to provide promotional aspects for the packaged item. Packaging can be for example, clear to show the packages item or colored to enhance the appeal of the product.
One important type of packaging includes clamshell packaging where a thermoplastic material is preformed to the basic shape of the item or product to be packaged. The item is then packaged by placing the item in the clamshell and closing the two halves of the clamshell over the package. The clamshell is preferably sealed by a heat-sealing process.
There are four main methods of heat sealing or welding presently in use: hot wedge, radio frequency (xe2x80x9cRFxe2x80x9d), ultrasonic, and hot air. In the hot wedge method, two fabric pieces are drawn across a hot iron (or wedge) and then are pressed together. This method may be performed by hand held press-type tools. These tools lend themselves to laborer injuries, such as carpal tunnel syndrome problems or other hand injuries, during repeated use. In addition, operators vary and the quality of the seal depends on the operator and the operator""s present condition. This introduces a large amount of variability in the packaging process.
The hot wedge method is quite similar to the hot air process with only the heat delivery system being different. Another disadvantage of this method is that the wedge can become contaminated with dirt and melted plastic which then reduces the amount of heat delivered to the seam. Further, hot wedge welders typically experience a hot section immediately after the beginning of the weld as the wedge accumulates excess heat when idle. Another disadvantage is that, since the heat energy must pass through a solid object to reach the seam, the maximum speed of the hot wedge welding process is limited by the thermal conductivity of the wedge.
The RF method is probably the most widely used approach for heat sealing. The RF welder is basically an antenna (the die) that is poorly matched to the amplifier, thereby producing a great deal of heat rather than radio waves between the antenna and the underlying plate. In practice, the two fabric pieces are laid on the plate. The die is then brought down, thereby pressing the two pieces together. The operator then initiates the welding process by pressing a pair of push buttons. The actual RF process takes from about 5 to 15 seconds, depending upon the thickness of the pattern pieces and the amount of RF energy available from the machine.
There are, however, several disadvantages to the RF method. RF welding is a slow process because the size of the die is limited by the available energy of the unit. Typical RF welding dies are about 1 to 3 feet in length and approximately xc2xd inch wide. There is also some concern about the operator""s health and safety as the operator is usually inches from an intense RF source which may be activated several hundred times in a typical shift. While RF health hazards have not been documented, it is known that stray RF energy from such machines can damage electrical equipment within approximately 50 feet of the machine and can light fluorescent fixtures located nearby. In addition, due to the die and plate arrangement, the RF method is typically limited to seams or joints that can be laid flat for welding. Three-dimensional dies and plates are occasionally used, but are quite expensive and require a vacuum or other methods to hold the fabric in position as the die is applied. Further, the Federal Communications Commission (xe2x80x9cFCCxe2x80x9d) has become increasingly strict regarding emissions of stray RF energy from industrial sources. Because of the increasingly strict FCC regulations, new RF welding equipment can typically cost $80,000 or more.
Ultrasonic welding is a process that is like RF welding, with the exception of the energy source. Rather than using radio waves, ultrasonic welding uses sound waves that basically vibrate the fabric molecules until sufficient heat is generated to melt the coatings.
In general, hot air welding is much faster than other methods, can accommodate three-dimensional patterns, and requires no dies or tooling. In a hot air welder, the flow of hot air that floods the seam is not subject to contamination, as with the wedge welder, and there is no initial drop off of heat at the beginning of the seam. Most fabricators want the speed of hot air technology, but have felt that it is difficult to obtain consistent results for many types of coated fabrics and also that it requires highly trained operators.
The typical rotary hot air welding apparatus uses hot air to join together two pieces of plastic coated fabric. The welder first injects a stream of hot air from a hot air nozzle between the two pieces of coated fabric. The temperature of the hot air can be set in the range of approximately 500 to 1350 degrees F. The fabric pieces are then pinched between and pulled through the apparatus by two drive wheels. The distance from the hot air nozzle and the pinch point between the two wheels is in the range of approximately 0.5 to 0.75 inch. The wheel speed determines how long the fabric is exposed to the hot air stream before it passes between the wheels. With a constant air temperature, the amount of heat energy delivered to the fabric is inversely proportional to the wheel speed; a faster speed decreases the exposure and vice versa.
Commercial hot air welders currently available on the market have a number of shortcomings. One shortcoming is the lack of accurate control of the speed of the two drive wheels. If the wheel speed varies from the required speed, then the amount of heat delivered to the seam will vary. Too much heat supplied to the weld results in burnt fabric while too little heat results in cold welds or unwelded fabric.
Therefore, a need exists for a heat sealer device that provides reliable and fast heat welds without the dangerous effects and expense of the prior art techniques. A further need exists for an easily operated apparatus that provides a consistent weld for a repeated manufacturing process.
A heat sealer includes a base configured to be mounted on a tabletop, a first jaw connected to the base, and a second jaw operatively aligned with the first jaw. An actuator is coupled to the second jaw to provide relative motion with respect to the first jaw. A heating device is coupled to the first and second jaws for heating the jaws to a set temperature to enable material to be contacted and welded when the first and second jaws are in a closed position.
Another embodiment of the heat sealer is employed for clamshell packages. The heat sealer includes a base configured to be mounted on a tabletop, a first jaw connected to the base, and a second jaw operatively aligned with the first jaw. An actuator is coupled to the second jaw to provide relative motion with respect to the first jaw. A heating device is coupled to the first and second jaws for heating the jaws to a set temperature to enable material to be contacted and welded when the first and second jaws are in a closed position. A casing is coupled to the base and encloses at least the first and second jaws and the heating device to prevent casual operator contact with the first and second jaws and the heating device.
In alternate embodiments of the present invention, the first jaw and the second jaw may include a non-stick liner. The actuator may be coupled to a guide rod to provide a controlled displacement between the first jaw and the second jaw. The sealer may include a timing device, which measures a time in which the first and second jaws are in the closed position. The sealer may include a pressure sensor, which measures the pressure and adjusts the actuator accordingly. The heating device is preferably controlled by feedback from a temperature measurement device. The sealer may include a sensor operatively positioned relative to the first jaw and the second jaw to sense a position of a clamshell package relative to the first and second jaws. The sensor preferably triggers the actuator to close the first and second jaws. The casing may include a guide which enables a clamshell package to be aligned with and disposed between the first and second jaws. The sealer may include a memory, which stores a plurality of settings combinations for different clamshell packages. The actuator may be coupled to a mechanism which simultaneously provides a rotational and translations motion to the first jaw.
A method for sealing a workpiece, includes the steps of configuring a heat sealer by adjusting at least one of temperature, pressure and engagement time of jaws, placing a package in the sealer by presenting one side of the package to be sealed into the sealer, and closing jaws of the sealer to engage the package in a hands-free weld operation. The method may also include the step of adjusting a trigger sensor, which triggers the jaws to close.
These and other objects, features and advantages of the present invention will become apparent from the following detailed description of illustrative embodiments thereof, which is to be read in connection with the accompanying drawings.